PROJECT SUMMARY/ABSTRACT There is a large gap in understanding the functions of vaporized nicotine products (VNPs); i.e. what they do and what exposures they achieve with each episode of use, and the extent to which this might vary and thus average out over time. This project is designed to answer a broad set of questions about the evolution of the nicotine delivery marketplace in countries with differing policy frameworks towards VNPs. Specifically, the proposed research revolves around three major questions: 1) How does the policy environment in a country affect the mix of product types and brands (both VNPs such as e-cigarette and conventional cigarette) used most commonly? 2) Does regulation of VNPs as a medicine versus recreational use affect VNP contents, labeling accuracy, nicotine emission and delivery, and unit variability? 3) Do product characteristics and/or brand preferences shift as VNP use changes with time? Surveillance of product characteristics during the project period will allow the investigative team to elucidate the potential roles of consumer preference, regulation, and larger market dynamics (e.g., mergers and acquisitions) in changes to product performance and brand share.